This invention generally relates to polymerization. It is more particularly concerned with a process for polymerizing novel homopolymers or copolymers from monomers of butene-1 and one or more of a variety of alpha-olefins having 2-10 carbon atoms preferably including ethylene, propylene, and mixtures thereof, which involves a critical selection of reaction conditions, reactants, reactant properties, and catalyst components.
As is well known to those familiar with the art, butene-1 and propylene can each be homopolymerized into crystalline polymers. Such homopolymers have been produced with an isotactic index (measured as the weight percent insoluble in boiling diethyl ether) in the order of 95-98.
The resultant polybutene-1 has two major crystalline forms. Upon cooling from the melt, there is formed a metastable crystalline modification known as "Form II." Over a period of time, usually several days, the Form II modification transforms into a stable modification known as "Form I." The transformation from Form II to Form I is accompanied by dimensional change in the polymer. The dimensional instability of polybutene-1 renders it disadvantageous for many applications. For example, films which are initially clear lose their optical clarity as the polymer changes crystalline form. Known processes for polymerizing butene-1 are taught in a variety of patents including U.S. Pat. No. 3,464,962 assigned to Mobil.
The current process allows for polymerization of 1-butene homopolymers or copolymers of butene-1 and ethylene at temperatures from 130.degree. F. to 160.degree. F. using a catalyst consisting of titanium trichloride, diethylaluminum chloride, and diethyl aluminum iodide where the molar ratio of aluminum to titanium is between 2:1 and 4:1 and the molar ratio of diethylaluminum chloride to diethylaluminum iodide is 1:1 to 3:1.
The problems with the current process include: (1) low catalyst activity which limits rates due to the deashing step; (2) effluent toxicity; and (3) slow crystallization transformation rate.
A new process for polymerizing butene-1 has been discovered which involves a critical selection of reaction conditions, reactant proportions, and catalyst components.
The process without iodide produces butene-1 polymers with a higher degree of crystallinity than those made with the aluminum diethyl chloride/aluminum diethyl iodide as the cocatalyst.
Accordingly, it is a broad object of this invention to provide a new process for producing such butene-1 homopolymers and copolymers by utilizing a more economical and an environmentally safer polymerization process which prevents iodide from getting into the waste streams.